Inhibition of aberrant proliferation and induction of apoptosis in pre-neoplastic human mammary epithelial cells by natural phytochemicals.
Aberrant proliferation and modulated apoptosis leading to impaired cellular homeostasis represent crucial early events in the multi-step carcinogenic process. Regulation of these perturbed biomarkers may predict efficacious prevention of cancer development. Present experiments on non-cancerous human mammary epithelial 184-B5 cells were designed to examine whether i) exposure to suspect environmental human carcinogen Benzo (a) pyrene (BP) alters the status of cell proliferation and apoptosis and ii) BP-induced alterations are modulated in response to select natural phytochemicals that inhibit rodent mammary tumorigenesis. Flow cytometric analysis, cellular immunoreactivity to proliferation specific and apoptosis specific gene products and anchorage-dependent colony formation represented quantitative endpoints. Cruciferous glucosinolate indole-3-carbinol (I3C), tea polyphenol (-) epigallo catechin gallate (EGCC) and soy isoflavone genistein (GEN) represented the chemopreventive test compounds. A single 24 h exposure to 39 lM BP resulted in a 50% decrease (P=0.02) in the ratio of quiescent (Q=G0) to proliferative (P=S + M) population in part due to increase in aberrantly proliferative cells. The BP-initiated cells also exhibited an 87.8% inhibition (P=0. 0001) in confluency-associated apoptosis and a concomitant decrease in cellular immunoreactivity to wild-type p53. Simultaneous treatment of cultures with BP + I3C, BP + EGCG and BP + GEN resulted in a 1.8- to 3.4-fold increase (P<0.01) in Q/P ratio and 1.8- to 6. 9-fold increase (P=0.001) in sub G0 (apoptotic) population. The induction of apoptosis was accompanied by enhanced p53 immunoreactivity (P<0.01). In long-term (21 day) experiments, BP treatment induced a 145.3% increase (P=0.001) in anchorage-dependent colony formation. This aberrant proliferation was inhibited by 44.2% to 65.3% (P=0.01) in the presence of the three phytochemicals. Thus, BP-induced aberrant proliferation is inhibited by the natural phytochemicals in part due to regulation of cell cycle progression and induction of p53 dependent apoptosis.
Katdare
M
M
Division of Carcinogenesis and Prevention, Strang Cancer Research Laboratory, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Osborne
M P
MP
Telang
N T
NT
D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001564:Benzo(a)pyrene / Q000633:toxicity*; D001940:Breast / Q000166:cytology / Q000187:drug effects; D001943:Breast Neoplasms / Q000473:pathology / Q000517:prevention & control*; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced / Q000187:drug effects*; D004785:Environmental Pollutants / Q000633:toxicity; D004847:Epithelial Cells / Q000187:drug effects; D005260:Female; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D011230:Precancerous Conditions / Q000473:pathology / Q000517:prevention & control*
D016588:Anticarcinogenic Agents; D004785:Environmental Pollutants; D007211:Indoles; D001564:Benzo(a)pyrene; D002392:Catechin; C045651:epigallocatechin gallate; C016517:indole-3-carbinol; D019833:Genistein